USSC has already addressed that at least somewhat in the 1936 Miller decision -- military weapons are the MOST protected and subject to the least restrictions, not the most restriction. That is what the prefatory clause is all about.

But if you read the full majority decision for Heller (both the actual holding and the dicta), you'll see that Justice Scalia argues right around a right to keep and bear "military" weapons and turns it into a right to keep and bear those "civilian" (non-military) weapons in common use. And he specifically states that this (in his opinion) is not contrary to Miller.